Make VM resolvePackageUri fail on package:foo and package:/foo.

runtime/bin/builtin.dart

Index: runtime/bin/builtin.dart
diff --git a/runtime/bin/builtin.dart b/runtime/bin/builtin.dart
index f0c0cdcf666adcbed7c9b14d0727df9ec4c35e7a..90213e89ce9535e2e304a8d3711829bd4992bf97 100644
--- a/runtime/bin/builtin.dart
+++ b/runtime/bin/builtin.dart
@@ -268,12 +268,12 @@ _setPackageRoot(String packageRoot) {
 
 
 // Given a uri with a 'package' scheme, return a Uri that is prefixed with
-// the package root.
+// the package root or resolved relative to the package configuration.
 Uri _resolvePackageUri(Uri uri) {
   assert(uri.scheme == "package");
   assert(_packagesReady);
 
-  if (!uri.host.isEmpty) {
+  if (uri.host.isNotEmpty) {
     var path = '${uri.host}${uri.path}';
     var right = 'package:$path';
     var wrong = 'package://$path';
@@ -281,7 +281,18 @@ Uri _resolvePackageUri(Uri uri) {
     throw "URIs using the 'package:' scheme should look like "
           "'$right', not '$wrong'.";
   }
-
+  var packageNameEnd = uri.path.indexOf('/');
+  if (packageNameEnd == 0) {
+    // Package URIs must have a non-empty package name (not start with "/").
+    throw "URIS using the 'package:' scheme should look like "
+          "'package:packageName${uri.path}', not 'package:${uri.path}'";

[Lasse Reichstein Nielsen, 2016/05/19 10:55:25]

This case wasn't handled before, but with a package root, it created a
completely wrong result.

+  }
+  if (packageNameEnd < 0) {
+    // Package URIs must have a path after the package name, even if it's
+    // just "/".
+    throw "URIS using the 'package:' scheme should look like "
+          "'package:${uri.path}/', not 'package:${uri.path}'";
+  }
   if (_traceLoading) {
     _log('Resolving package with uri path: ${uri.path}');
   }
@@ -294,7 +305,7 @@ Uri _resolvePackageUri(Uri uri) {
   } else if (_packageRoot != null) {
     resolvedUri = _packageRoot.resolve(uri.path);
   } else {
-    var packageName = uri.pathSegments[0];
+    var packageName = uri.path.substring(0, packageNameEnd);
     var mapping = _packageMap[packageName];
     if (_traceLoading) {
       _log("Mapped '$packageName' package to '$mapping'");
@@ -303,14 +314,8 @@ Uri _resolvePackageUri(Uri uri) {
       throw "No mapping for '$packageName' package when resolving '$uri'.";
     }
     var path;
-    if (uri.path.length > packageName.length) {
-      path = uri.path.substring(packageName.length + 1);
-    } else {
-      // Handle naked package resolution to the default package name:
-      // package:foo is equivalent to package:foo/foo.dart
-      assert(uri.path.length == packageName.length);
-      path = "$packageName.dart";
-    }
+    assert(uri.path.length > packageName.length);
+    path = uri.path.substring(packageName.length + 1);
     if (_traceLoading) {
       _log("Path to be resolved in package: $path");
     }